Solve the system by the elimination method 7x+5y=-25 5x+3y=-23

Mathematics

1 answer:

aksik [14]3 years ago

5 0

Step-by-step explanation:

7x+5y=25 ×3 7×-1.5+5y=25

5x+3y= -23 ×5 -10.5 +5y =25

5y= 25 + 10.5

21x+15y=75 5y= 35.5

25x+15y=69 y= 7.1

-4x=6

x=-1.5

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The General Social Survey asked a large number of people how much time they spent watching TV each day. The mean number of hours

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Answer:

Yes, we can conclude that the population standard deviation of TV watching times for teenagers is less than 2.66

Step-by-step explanation:

H0 : σ² = 2.66²

H1 : σ² < 2.66²

X²c = (n - 1)*s² ÷ σ²

sample size, n = 40

Sample standard deviation, s = 1.9

X²c = ((40 - 1) * 1.9²) ÷ 2.66²

X²c = 140.79 ÷ 7.0756

X²c = 19.897

Using a confidence level of 95%

Degree of freedom, df = n - 1 ; df = 40 - 1 = 39

The critical value using the chi distribution table is 25.6954

Comparing the test statistic with the critical value :

19.897 < 25.6954

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Hence, we can conclude that the population standard deviation of TV watching times for teenagers is less than 2.66

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3 years ago

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